The present invention relates to improvements in structures for forming a fibrous web from a suspension of fibers in a stock, and particularly to a headbox for handling a stock formed of a generated foam or a high consistency paper making stock.
In the manufacture of fibrous webs, particularly from synthetic fibers, one method which has been developed involves suspending the fibers in a foam suspension. The system for one such arrangement is disclosed in U.S. Pat. No. 3,716,449.
In handling the foam generated by the process taught in the aforesaid patent, a requirement is that the foam not be permitted to break down so that the fibers are uniformly carried and uniformly distributed. To accomplish this, the foam must be uniform and even in the bubble formation and this can be accomplished by continual regeneration of the foam in its flow through the system toward the forming surface.
In supplying the foam with the fibers suspended therein, its flow must be controlled so that the desired amount of fibers are fed to the forming surface at the speed desired. For the formation of a thicker web, a greater quantity of foam is supplied carrying a larger number of fibers onto the forming surface. The supply of fibers delivered to the forming surface also must be increased when the speed of the forming surface is increased. Likewise, for thinner web or a slower operating speed, the amount of foam fed to the forming surface is decreased.
The foam is generally supplied through a headbox arrangement. In the process the foam is first generated with the fibers distributed throughout the foam, and the foam is then flowed through a control headbox onto the forming surface. The control headbox optimumly must maintain uniformity of flow of the foam therethrough for uniform distribution of the foam out of the slice opening from the slice chamber. Also optimumly, a breakdown of the foam must be prevented and for a good procedure, foam regeneration should take place wherever possible throughout the system until the foam is delivered onto the forming surface.
It is accordingly an object of the present invention to provide an improved headbox for handling the flow of foam and delivering a uniform controlled supply of foam onto a forming surface where the flow can easily and readily be controlled.
A further object of the invention is to provide a foam flow headbox which provides for constant regeneration of the foam in the flow therethrough.
A still further object of the invention is to provide an improved foam supply headbox for the formation of a fibrous web in which the flow of foam is maintained uniform throughout the headbox and the quantity of foam flowing through the headbox can easily and quickly be controlled by the provision of a unique structure.
A further object of the invention is to provide a headbox of improved structure capable of handling a high consistency paper making stock.
Other objects, advantages and features, as well as equivalent structures which are intended to be covered herein will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiment in the specification, claims and drawings, in which: